The study you linked has this though, and it's astounding ...
Nor surprisingly, public trust in American elections fell sharply; for example, the Gallup World Poll reports that in 2016 a third of Americans (30%) expressed confidence in the honesty of their elections, down from a majority (52%) a decade earlier.85
That is not what I would call "public confidence in the election system." That is the public epressing they believe the election system is not honest.
I honestly didn’t look for one by the DHS, just one from March.